Transmission, particularly for use in a timepiece, for converting the oscillating movement of a tuning fork into a rotating movement

ABSTRACT

A transmission, particularly for use in a timepiece, for converting the oscillating movement of a tuning fork into a rotating movement, wherein a driving element in diving engagement with an indexing wheel is mounted on a driving rod rigidly fixed to one branch of the tuning fork for obtaining a substantially rectilinear movement of said driving element in spite of nonrectilinear oscillation of said tuning fork.

United States Patent Raval [54] TRANSMISSION, PARTICULARLY FOR USE IN ATIMEPIECE, FOR CONVERTING THE OSCILLATING MOVEMENT OF A TUNING FORK INTOA ROTATING MOVEMENT Gaston Raval, La Neuveville, Switzerland Omega LouisBrandt & Frere S.A. Biel, Beme, Switzerland Feb. 6, 1970 Inventor:

Assignee:

Filed:

Appl. N0.:

[30] Foreign Application Priority Data Feb. 19, 1969 Switzerland..2477/69 US. Cl. ..3l0/2l, 58/23 TF, 58/116 M, 3l0/25 Int. Cl. ..H02k7/06 FieldofSearch ..3l0/25, 37, 20,2l,22;58/23, 58/116, 121, 122, 27;74/15, 88

[ 5] Mar. 14, 1972 [56] References Cited UNITED STATES PATENTS 1,403,7671/1922 Goff. ..310/21 3,283,495 11/1966 Hetzeletal ..58/23 3,410,081ll/l968 Kuefier ..sa/23 3,486,049 12/1969 Hetzel ..31o/2s 2,690,64610/1954 Clifford ..58/ll6 FOREIGN PATENTS OR APPLICATIONS 470,017 4/1969Switzerland ..58/23 Pn'mary Examiner-J. D. Miller Assistant Examiner-B.A. Reynolds Attorney-Imirie and Smiley [57] ABSTRACT A transmission,particularly for use in a timepiece, for converting the oscillatingmovement of a tuning fork into a rotating movement, wherein a drivingelement in diving engagement with an indexing wheel is mounted on adriving rod rigidly fixed to one branch of the tuning fork for obtaininga substantially rectilinear movement of said driving element in spite ofnonrectilinear oscillation of said tuning fork.

10 Claims, 2 Drawing figures PATENTEDMAR 14 I972 3,649,858

I U101 O TRANSMISSION, PARTICULARLY FOR USE IN A TIMEPIECE, FORCONVERTING-THE OSCILLATING MOVEMENT OF A TUNING FORK INTO A ROTATINGMOVEMENT BACKGROUND OF THE INVENTION This invention relates to atransmission for converting an oscillating movement of a tuning forkinto a rotating movement, comprising at least one driving element indriving engagement with an indexing wheel and to which the oscillatingmovement of said tuning fork is transmitted. Said driving element may bea stepping pawl acting onto a ratchet wheel or a ferromagnetic elementacting onto a track of ferromagnetic material of the indexing wheel bymagnetic forces without touching it. In transmissions of this kind it isdesirable to attach the driving element to a portion of the tuning forkas distant as possible from the nodal point of the tuning fork in orderto impart to this driving element an amplitude as high as possible.However, it is generally known that the portions of the tuning forkhaving the greatest distance from the nodal point, that is, the freeends of the branches of the tuning fork, not only oscillate with thegreatest amplitude during normal operation, but also have the highestamplitude of disturbing oscillations occurring due to shocks acting ontothe timepiece. Therefore, driving elements fixed to the free ends of thebranches of the tuning fork are liable to produce faulty advance of theindexing wheel due to disturbing amplitudes of substantial magnitude ofthe branch ends of the tuning fork.

Particular problems are encountered with a magnetic transmission whereina magnetized oscillating driving element faces a profiled track offerromagnetic material of the indexing wheel. In order to obtain a highefficiency of such a system the airgap between the driving element andthe indexing wheel should be very small, but in this case the drivingelement might easily bump against the indexing wheel when the free endof the tuning fork is deviated by shocks acting onto the timepiece.Further, the magnetized driving element should execute an oscillatingmovement as rectilinear as possible. However, it was found that theoscillating movement of the free ends of the branches of a tuning forkis not sufficiently rectilinear, particularly when the branches of thetuning fork are of circular form or another curved form which isadvantageous for tuning forks to be used in timepieces. It is thusdifficult or practically impossible to make use of a transmission ofgood efficiency and reliability with a magnetized driving element, ifthis element is directly fixed to the free end of one of the branches ofthe tuning fork.

SUMMARY OF THE INVENTION This invention aims in mounting said drivingelement in such a manner that its oscillating movement is practicallyrectilinear and has an amplitude nearly as important as the free ends ofthe branches of the tuning fork, but that the disturbing amplitudes ofthe driving element are much smaller that those of the free ends of thebranches of the tuning fork when shocks act onto the timepiece. This aimof the invention is achieved broadly by fixing said driving element on adriving rod rigidly mounted on one branch of the tuning fork between thenodal point and the free end of said branch.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I, shows a preferred embodimentof the transmission according to the invention, and

FIG. 2, shows a modification of the transmission including a curveddriving rod.

The tuning fork whereof a portion is illustrated, FIG. 1 has a mountedbase I connected to the nodal point 2 of the tuning fork by a bridge 3of reduced cross section. The branches 4 of the tuning fork are ofsubstantially circular form. Their annular length is in the order of 90and their free ends 5 are directed inwardly. A pot 6 of soft iron with apermanent magnet 7 is fixed to each end portion 5 of the tuning fork(one only being shown). A coil disposed in the airgap between magnet 7and pot 6 serves as a driving coil or control coil connected to anamplifier sustaining the oscillation of the tuning fork 4.

A straight driving rod is rigidly fixed to the one branch 4 of thetuning fork between its free end and its nodal point. In the illustratedexample this rod 8 is fixed to the branch at a distance of about 40 fromthe nodal point 2, and the rod 8 has an inclination of about 9 to 10towards the center or symmetry axis of the tuning fork. The free end ofthe driving rod 8 carries a support 9 whereon is fixed a permanentmagnet 10 having two poles 10a, 10b. These poles 10a and 10b face thecircumference of an indexing wheel 11 mounted on a shaft 12. Asindicated, the rotating movement is transmitted by a worm 13 on shaft 12and a wheel 14 meshing therewith to the hands of the timepiece. Support9 is disposed near pot 6, that is, near the free end of the left branch4 of the tuning fork, but there is no direct connection between theseparts. Therefore, support 9 and magnet 10 may oscillate at an amplitudeand in a direction entirely independent of the amplitude and directionof the oscillation of parts 5 and 6. It was found that for the design asillustrated in the drawing, parts 9 and 10 will execute a practicallyrectilinear oscillating movement in a direction parallel to the axis 12,while parts 5, 6 and 7 oscillate along practically circular curves ofsmall radius with their center approximately in the center of gravity ofparts 4 to 7. Of course the rectilinear oscillation of support 9 is moresuitable for driving the magnet 10 than the substantially circularoscillation of portions 5 and 6. In addition it was found that thedeviations of the branches of the tuning fork under shocks acting ontothe timepiece are of much greater amplitude than the deviations ofsupport 9 under the same conditions. On the other hand, the oscillatingamplitude of support 9 of which the distance from the nodal point 2 isnearly equal to the distance of portions 5 and 6 from the nodal point,is practically in the same order as the amplitude of the free ends ofthe branches of the tuning fork. In this way an efficient and reliabletransmission is obtained for converting the oscillating movement of thetuning fork into a rotating movement. Other forms of the tuning fork, ofthe driving rod and of the driving element are feasible. Instead ofusing a magnetized driving element together with a nonmagnetizedprofiled track of ferromagnetic material on the driving wheel, the trackmay be magnetized instead, or the driving element and the track may bemagnetized. Further, another type of driving element, for instance, astepping pawl may be used. Instead of using a straight driving rod 8, acurved driving rod 8 bypassing obstacles may be provided as shown inFIG. 2.

What I claim is:

l. A transmission for converting an oscillating movement of a tuningfork into a rotating movement comprising:

a magnetically driven indexing wheel;

a rigid driving rod, rigidly mounted at one end thereof to one branch ofsaid tuning fork at a point of said fork between the nodal point and thefree end of said branch; and

a driving element magnetically engaged with said wheel for effectingdriving thereof, said element being rigidly mounted upon the oppositeend of said rod, the oscillations of said rod end oscillating saiddriving element to effect said magnetic drive of said wheel.

2. A transmission according to claim 1, wherein said driving rod isfixed nearer to said nodal point than to said free end.

3. A transmission according to claim 1, comprising a straight drivingrod.

4. A transmission according to claim 1, comprising a curved driving rodfor bypassing obstacles.

5. A transmission according to claim 1, wherein said indexing wheel hasa profiled track of ferromagnetic material, said driving element actingonto said track and indexing wheel respectively by magnetic forces.

6. A transmission according to claim I, wherein said tuning fork hascurved branches for instance circular branches, carrying driving magnetsfor sustaining the oscillation of the tuning fork.

of said driving element from the nodal point of the tuning fork beingsubstantially the same as the distance between the nodal point and thefree end of said branch.

10. A transmission according to claim I, wherein said rod extends towardsaid free end of the branch with the free end of the rod and saiddriving element, respectively, in proximity of said free end of thebranch.

t i i i

1. A transmission for converting an oscillating movement of a tuningfork into A rotating movement comprising: a magnetically driven indexingwheel; a rigid driving rod, rigidly mounted at one end thereof to onebranch of said tuning fork at a point of said fork between the nodalpoint and the free end of said branch; and a driving elementmagnetically engaged with said wheel for effecting driving thereof, saidelement being rigidly mounted upon the opposite end of said rod, theoscillations of said rod end oscillating said driving element to effectsaid magnetic drive of said wheel.
 2. A transmission according to claim1, wherein said driving rod is fixed nearer to said nodal point than tosaid free end.
 3. A transmission according to claim 1, comprising astraight driving rod.
 4. A transmission according to claim 1, comprisinga curved driving rod for bypassing obstacles.
 5. A transmissionaccording to claim 1, wherein said indexing wheel has a profiled trackof ferromagnetic material, said driving element acting onto said trackand indexing wheel respectively by magnetic forces.
 6. A transmissionaccording to claim 1, wherein said tuning fork has curved branches forinstance circular branches, carrying driving magnets for sustaining theoscillation of the tuning fork.
 7. A transmission according to claim 6,wherein said branches have an angular length in the order of 90*, saiddriving rod being fixed to the one branch at a distance in the order of40* from said nodal point.
 8. A transmission according to claim 7,wherein said driving rod is inclined by an angle in the order of 10*towards the axis of symmetry of said tuning fork.
 9. A transmissionaccording to claim 1 wherein the distance of said driving element fromthe nodal point of the tuning fork being substantially the same as thedistance between the nodal point and the free end of said branch.
 10. Atransmission according to claim 1, wherein said rod extends toward saidfree end of the branch with the free end of the rod and said drivingelement, respectively, in proximity of said free end of the branch.